1. Field of the Invention
The invention relates to an apparatus and a method for detecting a scanning range when applying the assistant frames with fixed sizes for the flatbed scanners.
2. Description of the Prior Art
For the optics system such as scanners, a tendency has formed gradually from only scan reflective documents to scan transparent documents. In the present days, the flatbed scanners scan transparent documents such as projection drawings or lantern slides by means of additional assistant frames as aided. However, a pre-scan is necessary to obtain the scanning range when applying conventional assistant frames. Unfortunately, this conventional scan method needs a long time interval to perform, and its precision also can not achieve our requirements.
Referring to FIG. 1A, wherein a conventional assistant frame 11 is applied in a flatbed scanner for scanning a scanned document 113 (lantern slides or the like) that is placed at the center of the assistant frame 11. Please note that the conventional assistant frame 11 includes a front mark 111 and a rear mark 112 allocated at the front and rear sides of the scanned document 113, respectively. The front mark 111 encompasses three transparent marks with upright triangle arrangement, and the rear mark 112 encompasses three transparent marks with downright triangle arrangement. A pre-scan is performed to make sure the shape and position of front mark 111 and rear mark 112 before scanning the scanned document 113.
FIG. 1B represents a conventional assistant frame 12 used for scanning multiple transparent documents, and holding holes 123 are further designed for putting in or taking out the transparent documents conveniently. A front mark 121 and a rear mark 122 are also respectively allocated at the front and rear sides of the assistant frame 12. Similar to the usage of the assistant frame 11, a pre-scan is also performed to make sure the shape and position of front mark 121 and rear mark 122 before the scanned document 124 is scanned.
Please note that whole the assistant frames described in the FIG. 1A and FIG. 1B must be scanned to obtain marks information at the positions of the front and rear marks when performing the pre-scan. A sequent recognition operation is also required to recognize whether the front and rear marks are scanned and detected. Furthermore, operations for marking the required scanning ranges must be repeatedly performed to each transparent document. It is quiet a troublesome work to repeat the aforementioned operations when many transparent documents need to be scanned. Additional time is thus needed before scanning the scanned documents, and furthermore, the conventional flatbed scanners must waste a long time interval to complete required scan operations. A need has therefore been arisen to disclose an apparatus and a method, in which the time interval of the pre-scan can be reduced when applying the assistant frames in the flatbed scanners.